Unloading devices of this type are needed in order to move piece goods kept in a temporary store as rows of products in so-called product carrier shuttles of a product store from the store onto outfeed belts. These product carrier shuttles mostly consist of four or six or even up to 24 product carrier trays, on which the product rows at the inlet of the temporary store are stored at a certain conveying speed.
In general, these are temporary stores that handle the product rows according to the First in First out (FiFo) principle. This operating principle is mostly applied to unpackaged products. The product carrier shuttles are rotatably suspended from two endless chain strands arranged in a pairwise manner. The distance between these product carrier shuttles on the chain is a function of the length and the height of the products. Also, the vertical distance of the respective product carrier trays within a product carrier shuttle is a function of the height of the product. The chain of a temporary store that is equipped with product carrier shuttles in a circulating manner is driven at the inlet thereof using a servomotor that is synchronized with the production rate, and is at the outlet also driven by a servomotor that is synchronized with the packaging rate.
The shuttle chain is here usually moved vertically upwards at the inlet of the temporary store and vertically downwards at the outlet thereof. However, in exceptional cases, this may also be the other way around. At the inlet of these temporary stores, there is a multiplicity of technical solutions known from the prior art, which allow the product rows arriving from production to be stored at a high rate. Here, the product rows are loaded onto the product carrier trays in a contactless manner only at their rate, so that the respective product row can slide onto the product carrier tray provided.
This means that at the outlet of the temporary store, the cycle rate has to be approximately 20% higher than at the inlet. Any faults along the packaging line, which are normally on the outlet side, result in an increase of the filling level of the temporary store. To ensure that this increase in filling level during production can be reduced again, the outlet of the temporary store must be capable of a cycle speed that is higher by that same 20%.
For discharging, the product rows are pushed out by a pusher from the product carrier trays onto the outfeed belt. In the process of this, the pusher penetrates the product carrier shuttle until the product row rests on the outfeed belt over its length. Subsequently, the pusher bar is retracted back by the same stroke. During this time, the product carrier shuttle cannot be moved. Mot until after the return stroke is completed can the next product carrier tray be provided again by a downward cycle of the chain of the temporary store. This process is time-consuming and considerably reduces the number of outlet cycles.